I think it's more like you behave differently around different people. With close friends, you confide more, be more at ease and show all your ugly habits. With colleagues and friends not so close to you, you tend to hold back and not talk about everything. You'll behave in a different manner, more serious one. With people you don't like, it is more like ying shiu the person, but you won't be paying the person much attention resulting in a bad impression fron the other party. But U don't mind cos U don't like him/her anyway.
I guess the faces you'll portray to others depends on the interest level you have in the other person.
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Aloha
Smile always